The Zaitsev variation of the Closed Spanish is a favorite line of many of the world's best chess players, including many World Champions. Until now, however, 'there has not been a compilation of the theory of the line, together with the relevant lines of the Breyer and Smyslov Variations into which play often transposes. This book is intended for experienced chess players rated 1700 and above. It contains. heavy-duty theory with many ideas simply credited to the appropriate sources and a good deal of unannotated games. The material is to be used for study of the opening and development of further ideas, as not: as a treatise with definitive evaluations. The Zaitsev variation reads to rich positional and tactical play which requires deep understanding of chess. The games produced in this line are therefore rather difficult to annotate, and many complete games have been provided without notes. The subtle nature of the variation has created profound chess and the author is faced with a difficult task - to read the minds of the great prayers of our time. Therefore I have consulted the players notes whenever possible. The reader is urged to consult the deeply annotated games which appear in collections of tournaments or biographical volumes. In order to accommodate the amount of prose required to explicate the ideas behind the opening play, I have resorted to a greater than usual use of Informant symbols, simply to save space in what would otherwise be a volume well longer than permitted in the hundred-page monograph format.